MODULATION-DOPED CD1-XMNXTE CD1-XMGYTE QUANTUM-WELL STRUCTURES WITH SPATIAL INPLANE PROFILING OF THE WELL WIDTH AND THE DOPING INTENSITY/

We report on the design and growth by molecular beam epitaxy of two ty pes of graded Cd1-xMnxTe/Cd1-yMgyTe quantum well structures having a p recisely controlled spatial profile of either the quantum well width a nd/or of the number of donors in one of the directions perpendicular t o the growth axis. The existence of a spatially varying quantum well w idth was demonstrated by different wavelengths of the photoluminesce e mitted from different regions of the sample. The presence of two-dimen sional electron gas with a spatially varying concentration produced by graded modulation doping was evidenced by magneto-optical studies whi ch revealed signatures of either excitons, or negatively charged excit on-electron complexes (X-), or Fermi-edge singularity, all in a single sample grown in one molecular beam epitaxy process. Such structures m ay be very useful for tunable wavelength radiation sources as well as in detailed studies of various physical characteristics of the quantum wells. (C) 1998 American Institute of Physics. [S0003-6951(98)01136-X ].